Electric circuit breaker with novel tripping assembly



J1me 1966 c. L. JENCKS ETAL 3,258,560

ELECTRIC CIRCUIT BREAKER WITH NOVEL TRIPPING ASSEMBLY Filed April 14, 1964 2 Sheets-Sheet l S 2 4 AL m a Q 7 3 a w ATTORNEY June 28, 1966 c. JENCKS ETAL 3,258,560

ELECTRIC CIRCUIT BREAKER WITH NOVEL TRIPPING ASSEMBLY Filed April 14, 1964 2 Sheets-Sheet 2 FIG.6

BY wmflrcuv A TTOE'NEY United States Patent ELECTRIC CIRCUIT BREAKER WITH NOVEL TRIPPING ASSEMBLY Charles L. Jencks, Avon, and Frank H. Murphy, West Hartford, Conn., assignors to General Electric Company, a corporation of New York Filed Apr. 14, 1964, Ser. No. 359,567 13 Claims. (Cl. 20088) The present invention relates to electric circuit breakers, and more particularly to electric circuit breakers of the type including movable contacts and operating mechanism for moving the contacts including a member releasable to cause automatic opening of the contacts, and means for holding the releasable member in a latched position under normal current conditions, plus means for causing release of the releasable member upon the occurrence of predetermined current conditions through the circuit breaker.

Electric circuit breakers of the type referred to have in recent years been provided with extremely compact operating mechanisms with high-strength operating springs, by means of which the current rating of such devices has been substantially increased. The overall reduction of size of such circuit breakers and the increase in the strength of operating mechanisms, however, have rendered prior latching and tripping arrangements disadvantageous in such devices because of the limited size and increased forces.

It is a general object of the present invention to provide a latching and tripping arrangement for an electric circuit breaker which is ultra-compact and capable of handling greatly increased forces.

It is another general object of the invention to provide an electric circuit breaker including a latching and tripping assembly which can be more easily manufactured and assembled than prior art types.

It is a particular object of the invention to provide a circuit breaker latching and tripping arrangement of the type including a molded trip bar which can be actuated by one of a plurality of circuit breaker poles wherein metallic latching means carried by the tripping bar can be readily added to the trip bar after the trip bar has been molded, and need not be molded as a part thereof or as an insert.

It is another object of the invention to provide a latch construction of the type described which provides a predetermined fixed amount of latch engagement automatically whenever the breaker is reset following tripping.

It is another object of the invention to provide an electric circuit breaker latching and tripping means including magnetically operable means disposed in a compact and efiicient arrangement.

More particularly, it is an object of the invention to provide an electric circuit breaker latching and tripping.

arrangement including magnetically operable tripping means which occupies a relatively narrow but relatively high space at the end of the circuit breaker casing so as to require no additional volume to be provided especially for this purpose in the circuit breaker casing.

It is a further object of the invention to provide an electric circuit breaker latching and tripping arrangement including a single supporting means, separate from the operating mechanism, for supporting a common trip bar and contact cross-arm. This is useful because the operating mechanism is positioned in only one pole, while both the contact cross-arm and the common trip bar extend across two or three poles. A much sturdier assembly is thereby provided by which both of these members are supported at their opposite ends.

It is an additional object of the invention to provide a multipole circuit breaker assembly in which a common trip bar can be readily assembled after all of the other parts are in place, by a simple snap-in type assembly.

In accordance with the invention in one form, a circuit breaker latching and tripping arrangement is provided including a common trip bar extending across all poles of a circuit breaker. A pivotally supported intermediate latch member is provided which engages and retains the releasable member of the circuit breaker operating mechanism. The intermediate latch member itself is retained by endwise engagement with a pin carried by the common trip bar. A second pin carried by the common trip bar engages the intermediate latch member to limit the amount of latch overlap on the first pin. The use of pins as described makes it possible to insert these members after the common trip bar has been molded and makes it unnecessary to have these parts molded as inserts.

In accordance with another aspect of the invention, a circuit breaker latching and tripping arrangement is provided which comprises a common trip bar and magnetically operable means for rotating the trip bar upon the occurrence of predetermined current conditions. The magnetic means comprises a magnetic field piece supported near the back wall ,of the breaker and a pivotally supported armature which is pivotally supported substantially directly above the magnetic field piece and which includes a pair of leg portions extending toward the magnetic field piece, the bight portion of the armature member being adjacent its pivoted portion. The magnetic assembly therefore occupies a greater dimension in the front to rear direction of the circuit breaker and only a relatively small dimension lengthwise of the circuit breaker.

The invention will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claims.

In the drawings,

FIGURE 1 is a side elevation view of an electric circuit breaker incorporating the invention, a portion of the side casing being broken away;

FIGURE 2 is a side elevation view of the latching and tripping portion of the circuit breaker of FIGURE 1;

FIGURE 3 is a perspective view of the latching mechanism of the circuit breaker of FIGURE 1;

FIGURE 3A and FIGURE 3B are perspective views of elements of the latching mechanism;

FIGURE 4 is an exploded perspective view of the contact cross-arm and common trip bar and the associated supporting means of the circuit breaker of FIGURE 1;

FIGURE 5 is a perspective view showing the magnetic tripping means of the circuit breaker of FIGURE 1, and

FIGURE 6 is an elevation view of the center portion of the trip bar of the breaker of FIGURE 1, showing the relative placement of the stop and latch pins.

In the drawings, the invention is shown as incorporated in a 3 pole electric circuit breaker of the molded-case type comprising an insulating casing including a base portion 10 and cover portion 11. The circuit breaker includes a pair of separable contacts (not shown) for each pole thereof adapted to be operated by a manually engageable handle 12 projecting from the cover member 11. The circuit breaker operating mechanism includes a releasable member 13 which is normally latched in the position shown in FIGURES 1 and 2 but which when released is movable to cause automatic opening of the circuit breaker contacts. The circuit breaker operating mechanism, not shown, may be of any suitable type, such for example as that shown in co-pending application Serial No. 372,193, filed June 3, 1964 in the name of Frank H. Murphy, and assigned to the same assignee as the present invention.

Referring to FIGURES 2 and 3, the releasable member 13 is normally restrained in the latched condition by means of a generally inverted-U-shaped intermediate latch member 14. The intermediate latch member 14 includes a pair of inwardly directed extensions 15 which, referring to FIGURE 2, are pivotally supported in openings 16 in side frame members 17 (only one shown) of the circuit breaker operating mechanism.

The releasable member 13 is biased upwardly as viewed in FIGURES 1 and 2 by means of the operating mechanism springs, not shown. The upward bias of the member 13, acts on the intermediate latch member 14 to bias it for rotation in a clockwise direction as viewed in FIG- URE 2.

Movement of the intermediate latch member 14 in clockwise direction is normally prevented in accordance with the invention by latching means comprising a latch pin 18 (see FIGURE 3) mounted in the insulating common trip bar 19, in a manner to be described. The common trip bar 19 is biased for rotation in a clockwise direction as viewed in FIGURE 2 by suitable means such as by tension spring 20 (see FIGURE 4). Rotation of the common trip bar 19 in a clockwise direction is limited by the engagement of an elognated stop pin 21 with an edge surface of the bight portion of the intermediate latch member 14, as shown in FIGURES 2 and 3.

As indicated, the engagement of the pin 21 with the intermediate latch member 14 determines the relative position of the latch pin 18 with the member 14. As shown in FIGURE 6, the pins 21 and 18 are mounted in the trip bar 19 in such a way that the pin 21 is tangent to a line LL passing through the center of the pin 18 and being parallel to the axis of rotation of the trip bar 19. Thus as shown, in the latched position, the pin 18 has approxi mately one-half its end area overlapping the intermediate latch member 14.

The end 18B of the pin 18 is curved on an are having its center on the axis of rotation of the trip bar 19. Because of this, the trip bar may be rotated toward tripping position without causing movement of the intermediate latch member 14 until tripping actually occurs.

For the purpose of causing rotation of the common trip bar 19 upon the occurrence of predetermined current conditions, both thermal and magnetic operating means are provided. The thermal operating means comprises an elongated bimetallic strip 23 which is rigidly mounted adjacent one end by suitable means such as by welding, to a heater strip conductive member 24. The heater member 24 is generally U-shaped and is connected between an incoming terminal strap 25 and a conductor 26 leading to the circuit breaker movable contact members (not shown). The terminal strap 25 supports a terminal connector member 27 having a clamping screw 27' for the purpose of connecting an incoming cable.

The current flow therefore, beginning at the connector 27, is as follows: from the connector 27 to the strap 25 to the heater member 24, to the conductor 26, and thence to the circuit breaker contact arm and contacts. Heat generated in the heater member 24 is carried by conduction to the bimetallic strip 23 which, when heated, warps so as to move the calibrating screw 29 to the left as viewed, and into engagement with the extension 19A of the trip bar 19. Continued movement of the bimetallic strip causes counterclockwise rotation of the trip bar 19, moving the latch pin 18 below the retaining edge 14A of the intermediate latch member 14. This permits the intermediate latch member 14 to rotate slightly clockwise as viewed in FIGURE 2, thereby releasing the releasable member 13 and causing automatic opening of the circuit breaker.

For the purpose of providing substantially instantaneous trip action, magnetic tripping means is provided, comprising a magnetic field piece 31, see FIGURE 5, which is partially surrounded by the U-shaped heater conductor 24.

A generally U-shaped armature member 32. of flat sheet metal is provided, which is pivotally supported by means of oppositely-directed lug portions 33, resting in notches 34 in the base 10. The armature member 32 includes a pair of generally parallel leg portions 35 which are bent at an angle intermediate thereof and include end portions 35A disposed and arranged to be attracted to corresponding portions of the magnetic field piece 31. The leg portions 35 of the armature 32 straddle the bimetallic strip 23, as shown particularly in FIGURE 2.

The armature 32 also includes a backwardly-directed lug portion 36 which serves to retain one end of a bias spring 37, the other end of which is hooked under the stationary field piece 31. The bias spring 37 biases the armature 32 for clockwise rotation about its pivotal supports 34. The armature 32 further includes a forwardlydirected lug portion 38 which is disposed and arranged to engage the extension 19A of the common trip bar 19 when the armature 32 is rotated in a counter-clockwise direction, such as when the ends 35A are attracted to the field piece 31.

It will be observed that pivot point of the armature 32 is disposed substantially directly over the stationary field piece 31, and that the armature member comprises a relatively thin flat sheet member with its plane disposed generally at right angles to the back wall 10A of the circuit breaker casing base 10. By means of this construction, the magnetic tripping assembly occupies only a relatively small space lengthwise of the circuit breaker, and as a matter of fact, does not require any further volume than would be required to house the thermal tripping means alone.

The common trip bar 19 is pivotally supported by means of pins 46 at each end thereof, see FIGURE 4, which pins are received in holes 41 of a pair of novel supporting plates 42. The supporting plates 42 each include foot portions 43 and 44, and an intermediate screw receiving portion 45 which is adapted to receive a mounting screw 46 inserted through the bottom wall of the casing 10 as shown particularly in FIGURE 1.

The supporting plates 42 also each carry a pivot pin 47 which is received in a corresponding hole 48 of a gen erally U-shaped contact arm member 49, which in turn is carried by a contact gauging cross-arm 50. Thus the contact-arm assembly, comprising the cross-arm 50 and the three contact arms 49, is pivotally supported for rotation about an axis co-axial with the pins 47.

It will be observed that the supporting plates 42 provide a simple and effective means for supporting both the common trip bar 19 and the contact cross-arm 50 in an extremely compact and effective manner, by means of which the contact cross-arm 50 is pivotally supported at its opposite ends independently of the operating mech anism which is supported by side plates 17.

In accordance with another feature of the invention, the supporting plates 42 include outwardly directed supporting lug portions 42A at the upper ends thereof. The lugs 42A rest in corresponding notches or miniature shelf portions, not shown, in the upper edge of the base portion 18 of the circuit breaker casing. The receiving notch in the base for the tabs 42A is preferably dimensioned so that a small amount of outward lateral movement is permitted. Accordingly, the parts are preferably assembled in the casing by assembling the support members 42 and the contact cross-arm assembly 50. The insulating trip bar 19 is then installed simply by spreading apart the upper ends of the supporting plates 42 and snapping the bearing portions 40 of the trip bar 19 into the corresponding holes 41. This greatly facilitates the assembly of the circuit breaker since fewer parts need to be handled at once, and since the common trip bar 19 is out of the way while the contact cross-arm and supporting plates are being inserted and mounted.

The intermediate latch member 14 includes an integral angularly extending tongue or extension 1413, and the releasable member 13 includes an enlarged end portion 13A. When the releasable member 13 is released by the intermediate latch 14, the intermediate latch member 14 is prevented from falling in beneath the releasable member 13, by means of the interengagement of the extension 1413 with the widened portion 13A of the releasable member 13, thus facilitating resetting of the circuit breaker.

It should be noted that the intermediate latch member is not acted on directly by any spring bias, but is substantially free floating, and is biased only by the force exerted on it by the latch and the stop pin 21 on the one hand, and the releasable member 13 on the other. Thus, for example, when tripping occurs, the intermediate latch member 14 is held in a slightly clockwise position from that shown in FIGURE 2, by the action of the extension 13A on the extension 14B. At this time, the latch pin 18 is also under the edge 14A of the intermediate latch member 14, and is biased upwardly by the trip bar bias spring 20 When the releasable member 13 is reset, by suitable means, not shown, and is moved downwardly beyond the position shown in FIGURE 2, the angle of the latch pin with respect to the edge 14B of the latch member 14 is such as to bias the intermediate latch member 14 in a counter-clockwise direction, causing it to slide off the end of the latch pin 18, allowing the trip bar 19 to rotate slightly clockwise until the stop pin 21 engages the edge portion 14B.

When the releasable member 13 is thereafter allowed to rise again following resetting, it engages the edge portion 14A of the intermediate latch member 14 and the parts are then once again in the latched condition as shown in FIGURE 2. It will be noted that, during resetting, when the releasable member 13A is depressed below the position indicated in FIGURE 2 (i.e., farther clockwise), if the intermediate latch member 14 does not come to rest against the end of the stop pin 18, the action of the releasable member 13 on the edge 14A, when it moves to the latched position shown in FIGURE 2, will be such as to bias the intermediate latch member 14 in a clockwise direction and against the end portion of the pin 18.

There are substantial advantages in utilizing the latch pin 18 and the stop pin 21 as compared to some other form of latch. Thus, it is essential that the latch member 18, as manufactured, be entirely free from rough edges or burrs, and that its retaining surface be highly polished. Such edges .and such polish are readily attainable on screwmachine-made parts, whereas with flat or fabricated parts, separate operations are required to provide such smooth surfaces. The construction shown provides an extremely simple pin member as a latching member which can be readily manufactured on high volume automatic machinery of the screw-machine type with the required high degree of smoothness needed for latching surface. In addition, the use of such a pin member makes it possible to mold the insulating common trip bar 19 without any metallic inserts, but with holes formed therein so that after the piece is molded, the pins 18 and 20 may be pressed into the trip bar.

In accordance with a preferred form of the invention, the latch pin 18 comprises a shouldered pin as shown for example in FIGURE 3B, having a relatively small projecting end portion 18A with a highly polished slightly rounded end 18B, and a relatively larger knurled portion 180, which facilitates mounting the piece in the trip bar. It will be observed that the pin 18 serves only as a latch pin, and receives force only endwise inwardly on the end portion 18B, such force tending to push the pin further into the trip bar 19. Since no sidewise or bending stress is exerted on the pin 18, there is no danger of its falling out of its mounting.

Stop pin 21 is preferably constructed as shown in FIG- URE 3A, and comprises a miniature rolled tubing. This member is pressed in tightly fitting relation in a corresponding mounting hole in the trip bar 19. Since this pin does not need to perform any latching function, its

surfaces do not need to be of high smoothness or polish, it need not be a screw-machine-made part, and is preferably formed in the manner'shown. Since the pin 21 is formed of a rolled tubing having a slightly open seam, it is resiliently received in common trip bar and there is no danger of its falling out even though it has a slight sidewise force exerted on it in the latched condition of the circuit breaker. It will be observed, nevertheless, that the force exerted on the stop pin 21 is only the force of the bias spring 20, which need not be very great.

While the invention has been described in only one particular embodiment, it will be readily apparent that many modifications thereof may readily be made, and it is therefore intended by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker comprising:

(a) a member releasable to cause automatic opening of said circuit breaker;

(b) an intermediate latch member normally restraining said releasable member, said releasable member biasing said intermediate latch member for movement in releasing direction;

(c) a rotatable trip bar;

(d) a first projection carried by said trip bar, said first projection engaging said intermediate latch member with a predetermined amount of latch overlap when said trip bar is in a predetermined holding position and preventing movement of said intermediate latch member in said releasing direction;

(e) means biasing said trip bar for rotation in a first direction to increase said amount of latch overlap;

(f) a second projection carried by said trip bar and engaging said intermediate latch member, said e11- gagement of said second projection with said intermediate latch member restraining said trip bar in said holding position with said predetermined amount of latch overlap at said first projection, and

(g) current responsive means acting on said trip bar upon the occurrence of predetermined current conditions to cause rotation of said trip bar in a direc tion opposite to said first direction to a position where said first projection is disengaged from said intermediate latch member to permit movement of said intermediate latch member in releasing direction.

2. An electric circuit breaker comprising:

(a) a releasable member releasable to cause automatic opening of said circuit breaker;

(b) a pivotally supported intermediate latch member havinga portion displaced from the pivot thereof releasably restraining said releasable member, said releasable member biasing said intermediate latch member for rotation in releasing direction about its said pivot;

(c) a rotatable trip bar;

(d) a latch projection carried by said trip bar and engaging said intermediate latch member adjacent an edge portion thereof with a predetermined amount of latch overlap When said trip bar is in a predetermined holding position, said engagement of said latch projection with said intermediate latch member preventing movement of said intermediate latch member in said releasing direction;

(e) means biasing said trip bar for rotation in a first direction to increase said amount of latch overlap;

(f) a stop projection carried by said trip bar and engaging said edge portion of said intermediate latch member adjacent said latch projection and restraining said trip bar in said holding position under the bias of said biasing means, and

(g) current responsive means acting on said trip bar to cause rotation of said trip bar in a direction opposite to said first direction to permit movement of said intermediate latch member in releasing direction upon the occurrence of predetermined current conditions.

3. An electric circuit breaker comprising:

(a) an insulating casing having opposed top and bottom walls, opposed side walls and opposed end walls; (b) a trip member movable to cause automatic opening of said circuit breaker;

(c) an elongated magnetic field piece supported in said casing adjacent said bottom wall and having pole portions at the opposite ends thereof;

(d) a generally U-shaped magnetic armature member supported for pivotal movement about an axis of rotation substantially farther from said bottom, wall than said magnetic field piece;

(c) said armature member having the bight portion of said U adjacent said axis of rotation and having the leg portions of said U extending generally perpendicular to said bottom wall and terminating adjacent said pole portions of said field piece respectively;

(f) an electrical conductor passing between said bight portion of said armature member and said field piece for creating a magnetic flux in said field piece, upon the passage of predetermined current through said conductor, tending to attract said end portions of said armature member, and

(g) means carried by said armature member adjacent said axis of rotation for engaging said trip member to cause releasing movement of said trip member upon attraction of said armature member to said field piece.

4. An electric circuit breaker including an insulating casing having opposed top and bottom walls, opposed side walls, and opposed end walls, magnetic tripping means comprising:

(a) a member movable to cause automatic opening of said circuit breaker;

(b) an elongated magnetic field piece supported adjacent said bottom wall and extending transversely between said side walls, said magnetic field piece having pole portions at the opposite ends thereof;

() a magnetic armature member of magnetic sheet metallic material, said armature member comprising a generally U-shaped plate having its major fiat surfaces disposed transversely between said side walls and pivotally supported for rotation about an axis extending transversely between said side walls and substantially directly above said magnetic field piece;

(d) said armature member having the bight portion of said U adjacent said axis of rotation and the leg portions of said U extending fro-m said axis toward said bottom wall and terminating adjacent the end portions of said magnetic field piece respectively;

(e) electrical conductor means extending between said bight portion of said armature member and said field piece whereby flux is created in said field piece tending to attract said leg portions of said armature member upon the occurrence of predetermined current conditions in said conductor, and

(f) means carried by said armature member adjacent said axis of rotation for engaging said movable member to cause tripping of said circuit breaker upon the occurrence of said predetermined current conditions.

5. An electric circuit breaker comprising:

(a) an insulating casing having opposed top and bottom walls, opposed side walls and opposed end walls;

(b) a trip member in said insulating casing movable to cause automatic opening of said circuit breaker;

(c) an elongated magnetic field piece supported in said insulating casing adjacent said bottom wall and transversely between said side walls, said magnetic field piece having pole portions at the opposite ends thereof;

(d) an armature member of magnetic sheet metallic material in said insulating casing, said armature member comprising a generally U-shaped member supported for rotation about an axis extending transversely between said side walls substantially directly above said magnetic field piece;

(e) said armature member having the bight portion thereof adjacent said axis of rotation and having parallel leg portions extending downwardly toward said bottom wall and terminating adjacent the opposite end portions of said magnetic field piece;

(f) an electrical conductor having opposite end portions attached to said bottom wall of said casing and having an intermediate portion extending over said magnetic field piece between said bight portion of said armature member and said field piece; 7

(g) an elongated bimetallic strip having an end portion thereof rigidly attached to said intermediate portion of said conductor member and having its other end movable, said bimetallic strip having a substantial portion thereof extending between the opposed side portions of said magnetic armature, and

(h) means carried by said movable end of said bimetallic strip for engaging said trip member, to cause movement thereof in tripping direction upon deflection of said bimetallic strip, and means carried by said magnetic armature member for engaging said trip member to cause movement thereof in tripping direction upon attraction of said armature member to said field piece.

6. An electric circuit breaker comprising:

(a) a member releasable to cause automatic opening of said circuit breaker;

(b) an intermediate latch member normally restraining said releasable member, said releasable member biasing said intermediate latch member for movement in releasing direction;

(c) a rotatable trip bar of insulating material;

(d) a latch pin carried by said trip bar, said latch pin comprising a first portion anchored to said trip bar and a second portion projecting from said trip bar, at least said second portion of said latch pin comprising a cylindrical metallic member engaging said intermediate latch member with a predetermined amount of latch overlap when said trip bar is in a predetermined holding position and preventing movement of said intermediate latch member in said releasing direction;

(e) means biasing said trip bar for rotation in a first direction to increase said amount of latch overlap;

(f) a second projection carried by said trip bar and engaging said intermediate latch member, said engagement of said second projection with said intermediate latch member restraining said trip bar in said holding position and determining said predeternined amount of latch overlap at said latch pin, an

(g) current responsive means acting on said trip bar upon the occurrence of predetermined current conditions to cause rotation of said trip bar in a direction opposite to said first direction to a position where said latch pin is disengaged from said intermediate latch member "to permit movement of said intermediate latch member in releasing direction.

7. An electric circuit breaker comprising:

(a) a member releasable to cause automatic opening of said circuit breaker;

(b) an intermediate latch member normally restraining said releasable member, said releasable member biasing said intermediate latch member for movement in releasing direction;

(c) a rotatable trip bar of insulating material;

(d) a latch pin carried by said trip bar, said latch pin comprising a first cylindrical portion tightly fitting in a corresponding hole in said trip bar and a second cylindrical portion projecting from said trip bar and engaging said intermediate latch member with a predetermined amount of latch overlap when said trip bar is in a predetermined holding position and preventing movement of said intermediate latch member in said releasing direction; (e) means biasing said trip bar for rotation in a first direction to increase said amount of latch overlap; (f) a stop pin carried by said trip bar, said stop pin comprising an elongated cylindrical metallic member having a first portion tightly received in a hole in said trip bar and a second portion projecting fromsaid trip bar and engaging said intermediate latch member to restrain said trip bar in said holding position with said predetermined amount of latch overlap at said latch pin, and (g) current responsive means acting on said trip bar upon the occurrence of predetermined current con ditions-to cause rotation of said trip bar in a direction opposite to said first direction to a position where said latch pin is disengaged from said intermediate latch mem'ber to permit movement of said intermediate latch member in releasing direction. 8. An electric circuit breaker as set forth in claim 7, wherein said trip bar is supported for rotation about a predetermined axis of rotation, said stop pin extending substantially at right-angles to said axis of rotation and having its outer surface tangentially meeting a line through the center of said latch pin and parallel to said axis of rotation of said trip bar, whereby said stop pin retains said trip bar in latched position with approximately onehalf of the end area of said latch pin in overlapped latched relation with said intermediate latch member.

' 9'. An electric circuit breaker comprising:

(a) an insulating casing;

' (b) a plurality of movable contact arms;

(c) a contact cross-arm;

(d) means rigidly attaching each of said contact arms to said contact cross-arm for movement simultaneously between open and closed circuit positions;

(e) operating mechanism for operating said contact cross-arm, said operating mechanism comprising a member releasable to cause automatic opening of said contact arms;

(f) latch means normally restraining said releasable member in latched position;

(g) a common trip bar extending generally parallel to said contact cross-arm;

(h) means carried by said common trip bar for causing release of said releasable member;

(i) current responsive means associated electrically with at least one of said contact arms for causing rotation of said common trip bar upon the occurrence of predetermined current conditions through said contact arm;

(j) means supporting said common trip bar and said contact cross-arm for pivotal movement in said casing about substantially parallel axes, said means comprising a pair of pivot supporting plates separate from said operating mechanism, each of said supporting plates pivotally supporting one end of said common trip bar and one end of said contact crossarm assembly, and means rigidly attaching said supporting plates to said casing.

10. An electric circuit breaker comprising:

(a) a generally rectangular casing of insulating material having opposed top and bottom walls, opposed side walls and opposed end walls;

(b) a plurality of side-by-side elongated contact arms;

(c) means ganging said contact arms for movement as a unit between open and closed circuit position comprising an elongated non-circular cross-section contact arm;

(d) said contact cross-arm extending substantially parallel to said bottom wall and transversely between said opposed side walls and closer to said bottom wall than said top wall;

(e) a common trip bar extending substantially parallel to said contact cross-arm, said common trip bar extending closer to said top wall than said bottom wall;

(f) operating mechanism for operating said movable contacts between open and closed circuit positions, said operating mechanism comprising a pair of side plates and a member releasable to cause automatic opening of said contacts;

(g) latch means normally restraining said releasable member;

(h) means carried by said common trip bar for causing release of said latch means upon predetermined rotation of said common trip bar;

(i) current responsive means associated electrically with at least one of said contact arms and causing rotation of said common trip bar in releasing direction upon the occurrence of predetermined current conditions through said contact arm;

(j) means supporting said contact cross-arm and said common trip bar for rotation about their respective axes, said means comprising a pair of pivot supporting plates separate from said mechanism side plates, said supporting plates having means for pivotally supporting said common trip bar and for pivotally supporting the contact cross-arm assembly.

11. An electric circuit breaker as set forth in claim 10 wherein said pivot supporting plates are each attached to said bottom wall of said casing at one end and extend from said mounted end toward said top wall, said common trip bar including projections extending axially at each end thereof, the upper end portions of said supporting plates being resiliently movable outwardly in a direction generally parallel to said axis of said common trip bar, said projections of said trip bar being removably received in bearings in said supporting plates, whereby said common trip bar may be assembled following assembly of said contact cross-arm and said supporting plates in said casing, by resiliently springing said upper end portions of said supporting plates away from each other and inserting said common trip bar.

12. An electric circuit breaker comprising:

(a) an insulating casing having opposed top and bottom walls, opposed side walls and opposed end walls;

(b) a plurality of movable contact arms extending substantially parallel to each other;

(c) ganging means rigidly connecting said contact arms together for movement in unison between open and closed circuit positions comprising a non-circular ganging bar having said contact arms rigidly mounted thereon;

(d) an elongated common trip bar extending substantially parallel to said ganging bar, said ganging bar being supported closely adjacent said bottom Wall of said casing and extending transversely of said casing between said opposed side walls;

(e) said common trip bar extending substantially parallel to said ganging bar, said common trip bar being spaced substantially farther away from said bottom wall of said casing than said ganging bar;

(f) operating means for operating the contact arm assembly between open and closed circuit positions comprising a pair of opposed mechanism side plates and a releasable member releasable to cause automatic opening of said contacts;

(g) latch means normally restraining said releasable member;

(h) means carried by said ganging bar for releasing said latch means to permit automatic opening of said circuit breaker;

(i) current responsive means associated with a plurality of said contact arms each of said current responsive means causing releasing movement of said common trip bar upon the occurrence of a predetermined current condition through its associated contact arm;

(j) means supporting said common trip bar and said ganging bar for pivotal movement about substantially parallel axis, said means comprising a pair of supporting plates separate from said mechanism side plates, each of said supporting plates comprising a member of sheet metallic material;

(k) means supporting each of said supporting plates in said casing so as to extend generally from said bottom wall toward said top wall, said supporting means comprising fastening means fixedly attaching a portion of each of said supporting plates to said bottom wall;

(1) each of said supporting plates including an outwardly directed projection adjacent its upper end;

(m) means slidably guiding each of said projections for movement in a direction generally parallel to said pivotal axis;

(n) said common trip bar being releasably supported by said supporting plates adjacent said upper ends thereof, whereby said common trip bar may be assembled following assembly of said ganging bar and said supporting plates in said casing by resiliently moving said upper end portions of said supporting plates outwardly to admit said common trip bar, said supporting plates resiliently returning to a normal position in which they retain said common trip bar.

13. An electric circuit breaker comprising:

(a) a generally rectangular insulating casing having opposed top and bottom walls, opposed side walls and opposed end walls;

(b) a plurality of side-by-side contact arms supported in said casing;

() means rigidly ganging said contact arms together for movement in unison between open and closed circuit positions, said ganging means comprising a non-circular ganging contact cross-arm having said contact arms rigidly connected thereto;

(d) operating mechanism for operating the contact cross-arm assembly, said operating mechanism comprising a pair of opposed side plates and a member releasable to cause automatic opening of said contacts;

(e) latch means normally restraining said releasable member;

(f) a common trip bar supported in said insulating casing and extending substantially parallel to the contact cross-arm assembly;

(g) means carried by said common trip bar for causing release of said latching means upon predetermined rotation thereof;

(h) current responsive means associated with at least one of said contact arms for causing releasing movement of said common trip bar upon the occurrence of predetermined current conditions through said contact arm;

(i) said contact cross-arm being supported in said casing closely adjacent said bottom wall;

(j) said common trip bar being supported in said casing for rotation about an axis substantiallyparallel to said contact cross-arm but spaced substantially farther from the bottom wall than said contact crossarm assembly;

(k) means supporting said common trip bar for rotation about said axis comprising a pair of supporting plates separate from said operating mechanism, each of said supporting plates comprising a member formed of sheet metallic material having a portion rigidly attached to said bottom wall and extending generally from said attached end toward said top wall;

(l) said supporting plates each having the upper end portions thereof resiliently movable outwardly of said common trip bar, and said common trip bar being releasably pivotally supported on said upper end portions of said supporting plates,

(m) whereby said common trip bar may be assembled after assembly of said operating mechanism and said supporting plates in said insulating casing by resiliently moving said upper end portions of said supporting plates outwardly a small amount to receive said end portions of said common trip bar.

References Cited by the Examiner UNITED STATES PATENTS 2,140,360 12/1938 Jennings 200 107 X 2,579,673 12/1951 Jackson 200-106 X 2,673,908 3/1954 Brumfield 200-88 2,892,054 6/1959 Walker et al. 200 88 3,180,953 4/1965 Zubaty 317198 X BERNARD A. GILHEANY, Primary Examiner.

T. D. MACBLAIN, Assistant Examiner. 

3. AN ELECTRIC CIRCUIT BREAKER COMPRISING: (A) AN INSULATING CASING HAVING OPPOSED TOP AND BOTTOM WALLS, OPPOSED SIDE WALLS AND OPPOSED END WALLS; (B) A TRIP MEMBER MOVABLE TO CAUSE AUTOMATIC OPENING OF SAID CIRCUIT BREAKER; (C) AN ELONGATED MAGNETIC FIELD PIECE SUPPORTED IN SAID CASING ADJACENT SAID BOTTOM WALL AND HAVING POLE PORTIONS AT THE OPPOSITE ENDS THEREOF; (D) A GENERALLY U-SHAPED MAGNETIC ARMATURE MEMBER SUPPORTED FOR PIVOTAL MOVEMENT ABOUT AN AXIS OF ROTATION SUBSTANTIALLY FARTHER FROM SAID BOTTOM WALL THAN SAID MAGNETIC FIELD PIECE; (E) SAID ARMATURE MEMBER HAVING THE BIGHT PORTION OF SAID "U" ADJACENT SAID AXIS OF ROTATION AND HAVING THE LEG PORTIONS OF SAID "U" EXTENDING GENERALLY PERPENDICULAR TO SAID BOTTOM WALL AND TERMINATING ADJACENT SAID POLE PORTIONS OF SAID FIELD PIECE RESPECTIVELY; 